Inelastic seismic response of diagrid structure under critical seismic zone due to bi-directional ground motion

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 9 Issue: 11 | Nov 2022 www.irjet.net p-ISSN: 2395-0072
© 2020, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 423
Inelastic seismic response of diagrid structure under critical seismic
zone due to bi-directional ground motion
Utsha Chowdhury1, Krishnendu Chowdhury2
1,2Assistant Professor, Department of Civil Engineering, K K College of Engineering & Management, Jharkhand,
India
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Abstract – The innovative diagrid structural system has emerged with an aesthetic architectural view in the design of tall
building structures. Nonlinear dynamic analysis is investigating the response of diagrid structural system under critical seismic
zone owing to bi-directional excitation has been reported. Furthermore, in this study, the seismic performance of square and
circular diagrid structures with different brace angles are compared to sustain the stability in critical seismic zone in India.
Seismically operated asymmetric structures are more vulnerable than symmetricstructuresbecauseofthecouplingoflateraland
torsional vibration. For this purpose, asymmetric system makes a challenging issue to determine the critical response of load
resisting elements for serviceability. Structures are generally experienced on degradation matter of stiffness and strength in the
event of strong seismic excitation. In that case, the structural deterioration occurs due to the external loads, clearlydemonstrates
that the elements have large amount of losses and fragility finitely. A broad conclusion presents in this study that to help the fine
tune of the seismic code provisions.
Key Words: Inelastic response, Seismic response, Bi-directional, Angle of brace, Near-fault, Critical zone.
1. INTRODUCTION
Seismic analysis of R/C structure is necessary aspect in the recent past. Generally, diagrid structure is light weight structure
compelling against gravity and also resisting the excess seismic loading, controlled as much as possible compared to other
complex structures reasonably. The Diagrid structures are composed oftriangulatedsectionswhich combattheseismicforces
by axial action of diagonals provided on periphery. Structural design for diagrid system is governedbyhorizontal forcedueto
lateral loads like earthquake, wind load etc. which resistible by the exterior and interior structural systems, usually braced
frame, shear wall core etc. In the diagrid structural system structural patterns can be utilized to optimize the performance of
structural members. Due to the rapid growth of population and increment of land values in all aspects,especiallyinurbanand
rural areas, it is the duty of a structural engineer to contrive the versatile performing structural systems. As a result, various
structural systems have erupted over the years throughout the globe. The analysis of diagrid structure and its performance
analysis at different angles has already been estimated by some researchers [1, 2]. The main veneration at which particular
circumference the extended maximum stories are exploited and deflected in diagrid system owing to seismic loading. But in
present system have paved the way for different methods of structural systems, the real challengeslieinprocuring thesystem
with high performance [3]. Whenever the soil in hilly region is stiffer or rocky, the inherent bond between soil and foundation
is anemic; there is a divesting chance to collapse the structure against earth excitationinIndia [4,41].Inconventional building
there will be allocated number of vertical columns. But in case of diagrid vertical columnsareput back bytheinclinedcolumns
that are the diagonals. Diagrids are the array of triangles which has the combined abilitytoresistgravityandlateral loads both
in a single action [5, 41-51]. The diagrid structures are stiffer, lighter in weight and have higher lateral seismic stability than
the conventional system [5-9, 41-51]. Due to the diagonal or horizontal hollow supporting members and its triangulated
arrangements, the lateral loads, vertical loads and distributions are easily countered [6-9]. We are not proclaiming that the
extenuation of stories in this structural system at this aberrant and amorphous area against seismic load. Hence, we are
looking forward for working the versatile seismic analysis. Diagrid is relatively a new structural system, the research work
done or available is quite limited. The main source for any data available for diagrid is forming the diagrid buildings that have
been constructed and there is only handful of them in the whole world [14-16]. A large number of studies have been made to
address the issue of vulnerability of diagrid system under earthquake loading [14-18]. Even through few researchers have
extensively studied this new system and put forth their findings, it is not enough to establish for seismic response of this type
of structural system with secondary bracing system [11, 21]. The seismic response in a structural system is now essential
parameter in recent design methodology. Generally, symmetric structuresarefoundtobelessvulnerabletoseismicloadingas
compared to asymmetric counterparts. Structures are found to behave symmetrically under lateral loading causes of
constraints owing to architectural and functional aspects. From the view of mechanics, symmetric occurs due to the
coincidence of the center of mass (CM) and center of stiffness (CS). In every part of sectionofstructure,stiffnessiseverywhere
same and make same sense but the response of element is major differed. On the other hand, asymmetric setback is another

major criterion to determine the seismic excitation of load resisting element of structure with the variation ofCMandCS.This
eccentric condition makes the critical response due todifferent parametersthatcreatetheultimate responseonMDOFsystem.
The performance analysis of the diagrid structure is already made by some researchers but the literature regarding this in a
critical seismic zone in India is still unknown. In this backdrop, this case study reckons to estimate the individual response in
different stories diagrid structures. The study may providea muchbetterunderstandingofthevulnerabilityofsuchsymmetric
diagrid system also for asymmetric system. Several eminent examples of diagrid structures in world history are showninFig.
1. Dr. Kyoung Moon monitored the dynamic interrelationship between technology and architecture in tall buildings and
assigned an initial step towards for diagrid structural system in 2007. Dr. Lenord studied the effect of shear leg in the diagrid
buildings and developed on the work done by Moon in 2005. Researchers concluded that the performance of structure three
times than the framed tube building in shear leg ratio and showed higher efficiency in carrying lateral load in high rise
buildings [9-13]. Differentiate with conventional framed tubular structures without diagonals, diagrid structures are more
virtual in minimizing shear deformation because they carry shear by axial action of the diagonal members [17], while
conventional framed tubular structures carry shear by the bending of the vertical columns. The diagrid structures have
significantly higher resistance against shear lag phenomenon than equivalent tubular structures [18]. Diagrid structure
consisting of diagonal struts and ties in the periphery and an interior core with various complex shape [19, 20]. This type of
structures is popular in many developed countries in the world but in India it is yet to gain importance. Researchers have
estimated the seismic performance factorthatis worthy wayforusingpushoveranalysisandIDA-basedprobabilisticapproach
comparison on diagrid tall structure. In that case IDA-based method gives significantly more rational value for reduction
coefficient [22, 23, 47]. Very recent researchers scrutinized that hanging on the seismic reliability of multilevel response
modification factor, for steel diagrid structure where steel is used 30-40% less than conventional structurethatismoresafety
[24-26]. Last but not the least, combination of shear link to dissipate the earthquake energywith plasticdesignanalysismodel
conclude that the shear link is excellently performed and adequate margin against collapse that is effective seismic force
resisting system [27-30, 34, 39]. Significant amounts of work have been done in this case, but the aperture indicates the
judgmental response of diagrid structure due to seismic synthetic bi-directional ground motions excitation, whether the
structure of different stories for symmetric and asymmetric systems withdifferentdiagonal bracinganglesinacritical seismic
zone IV in India. Moreover, different parameters are considered and lie in a feasible range for diagrid response in the inelastic
range. It is also intended to investigate the effect of incorporation of bidirectional interaction for both systems in terms of
displacement of edge lateral load resisting elements. From this point of view, we can study the displacement and story drift
demand due to seismic excitation in inelastic response for the satisfactory of this effectiveness in critical phase that shouldbe
useful for practical and design purposes and is believed to be new.
Fig. 1. Example of diagrid structures. (a) Alder Headquarters, Qatar (b) Swiss Re Building, London (c) Hearst Tower, New
York (d) GOB Building, India.
2. IDEALIZED MODEL STRUCTURES
In this paper, model structures are represented for symmetric systems in eleven, twenty-one and thirty-one storiesofdiagrid
structures with various slopes (35°, 45° and 55°) of the external braces and alsoaneleven-storyasymmetricsystemwitha 55°
brace angle respectively. The idealized structures have a 30 m × 30 m for square plane system and a diameter of 35 m for
circular plane systems, as shown in Fig. 2, for preparing the response comparison respectively also 35 m × 40 m for
asymmetric plane system shown in Fig. 3 is considered. The height of each floor is 3.5 m. In this system, rigid floor diaphragm
is considered for both cases having three degree of freedom that is two translational degree of freedom along two principal
direction and one rotational in plane. In diagrid structures, a pair of braces are located at 6 m spacing for circular model and
a b c d

external columns are spaced at 3 m for square and rectangular diagrid structure along the perimeter. The given model is
assumed to have two lateral load resisting elements for both structural systems for outer and inner sides. In mid position,
column is satisfied as an element and as another element slab of floors is considered. Fig. 4 depicts the side elevation of the
different brace angles model structures. These inclined members i.e., diagonal braces are placed on a fixed support at earth
level to height of story levels that resist the shear-bending. Due to inclined brace members,lateral loadsarecounteredbyaxial
exertion of the brace tubes. The internal frames are designed for gravity load and thus dispense the pin-joint connection.
Fig. 2. Plan elevation of idealized symmetric structural system.
Fig. 3. Plan elevation of idealized asymmetric structural system.

Fig. 4. Diagrid model structures for different braces angle.
The mass of such elements is assumed to be zero and denoted by m. The lateral period(Tl),mass(m)andlateral stiffness(k)of
all elements for both systems were calculated using eq. 1., Where, m is lumped mass of story, Kl is the total lateral stiffness
2 /
l l
T m k
  ……[1]
in any principal directions = 4k, k is the stiffness of element in any directions for both cases. The degree of freedom of rigid
diaphragm is varied with different rigid floors. For the reference symmetric system, the location of CM and CS are initially the
same. Besides that, keep in touch on the lateral load resisting edge elementsofbi-directionallyasymmetricsystemeccentricity
is initiated by increasing the stiffness of one edge element and decreasing that of the element at the opposite edge. The lateral
load-resisting edge elements with less stiffness were considered like flexible elements and the oppositeedge elementshaving
greater stiffness were represented to as stiff elements. In this system, the location of the CM and CS recline at the different
eccentric location and assume on a same axial section. In such bi-directionally asymmetric systems eccentricities are
symbolized by ex and ey that lies between the distance of CM and CS with respect to principal axis of system. Distribution of
eccentric condition is balanced for both eccentricities’ ex and ey with the positive sense where CS and CM lies in the first
quadrant. Another observation shows that the negative eccentric sense that is ex and -ey where CM and CS lies in the second
quadrant of the principal axis of the system. Such this study gives an idea aboutthe natureofeccentricitymakesanydifference
or not in the behavior. The stiffness and mass of all floors in different storiesisvaried, wheremassofdifferentfloorsgenerated
by several parameters. A range of symmetric and asymmetric systems with an otherwise same fundamental parameter has
been studied.
3. METHODOLOGY
The non-linear equation of motion show in eq. 2. is numerically solvedintimedomainusingNewmark’sβ-γmethod andbythe
by modified Newton-Raphson technique is used for iteration. The Newmark’s parameters are chosen as γ = 0.5 and β = 0.25
[31, 33, 37-40]. The results are computed with various sizes of time step given by Tx/N, where Tx is the uncoupled lateral
period and N is an integer number which is gradually increased by doubling it to obtain the results with better accuracy. For
this purpose, we considered time step of Tx/400 for appropriate determination of values [31, 33, 37].Seismosignal V.5.1.0– A
computer program that constitutes an easy and efficient way for signal processing of strong-motion data [online]; 2018, ed:
available from URL: (http://www.seismosoft.com) and by the by added the essential parameters that is moment magnitude,
closest site-to-fault-rapture distance, shear wave velocity, mean time period [32]. Using this essential software investigating
the ultimate characteristic of ground acceleration motion capacity that has been acted on the structural diagrid members as
well as the different angle of braces that lies in joint connection. Where, r is the radius of gyration of mass of rigid deck;cisthe
damping matrix; ux, uy, θ are the translations of CM along the x and y axis and rotation of CM is horizontal plane respectively
and ügx and ügy are ground accelerations along two perpendicular principal axes respectively.

.. .
..
.. .
2 2
.. . ..
0 0 0 0 ( )
0 0 [ ] { } 0 0 0
0 0 0 0
( )
x x
gx
s
gy
y y
u u
m m u t
mr C f mr
m m
u u u t
 
   
 
   
     
     
   
   
     
   
     
   
   
     
 
   
….[2]
For symmetric system the uncoupled torsional effect is negligible.
4. GROUND MOTION
For the diagrid structural model an enhanced nonlinear dynamic analysis has been used which is capable to capture
progressive seismic damage of structures. As scaled near-fault (NF) ground motions are considered from Pacific Earthquake
Engineering Research(http://peer.berkeley.edu) Centerfortheperformanceanalysis [37].Thegroundmotionisgeneratedon
a structural system like a vector formation, often oriented in north-south (N-S) and east-west (E-W) directions whereas the
strong motion database for horizontal componentsofmotionsaregenerallyavailablealongorientationsof recordingwhichare
often arbitrary. This recorded component is applied along two principal axes of the structure with the shearing brace effect.
Thus, it is often deduced that the arbitrarily placed recording sensors are aligned with the principal axes of structure. In this
way, overall structural response of the MDOF diagrid system is estimated owing to bi-directional NF syntheticgroundmotion
history under critical zone IV. The case studies in this paper are investigated for a set of fifteen bi-directional syntheticground
motions to resist any variability arising subjected to the particular characteristic of any specific ground motion. Details of the
ground motions are shown in Table 1. We select ground motions in termsofgeophysical parameters,viz.,magnitude-distance-
soil conditions triads. Selected motions are scaled appropriately to introduce a uniform level of inelastic action. For each
component of a motion, this scale factor is decided observingthespectral accelerationofeachoriginal recordcomponentat the
fundamental period of vibration of element in relation to the element capacity. Scale factors of two components of a recordso
computed are compared and the average factor is applied to the components.
Table 1: Details of ground motions (NF) used.
Serial
no.
Event (Year) Station Record ID
Moment
magnitude
(Mw)
r(km) Vs30(m/s)
PGA(m/s2) Tm(s)
X -
Component
Y -
Component
X -Direction Y- Direction
1.
Corinth_
Greece,
1981
Corinth
RSN313 6.6 10.27 361.4 2.32 2.90 0.17 0.14
2.
Landers,
1992
Joshua Tree RSN864 7.3 11.03 379.32 2.68 2.78 0.73 0.78
3.
Landers,
1992
Morongo
Valley Fire
Station
RSN881 7.3 17.36 396.41 2.19 1.61 0.69 0.88
4.
Manjil_
Iran,1990
Abbar
RSN1633
7.4 12.55 723.95
5.04 4.87 0.32 0.33
5.
Tottori_
Japan,2000
OKY004
RSN3907 6.7 19.72 475.8 8.08 5.28 0.20 0.18
6.
Chuetsu-oki_
Japan,2007
Yoshikawak
u Joetsu City
RSN4850 6.8 16.86 561.59 4.44 3.08 0.79 0.83
7.
Iwate_
Japan,2008
MYG005
RSN5664 6.9 13.47 361.24 5.25 4.37 0.78 1.76
8.
Iwate_
Japan,2008
Kurihara
City
RSN5818 6.9 12.85 512.26 6.89 4.14 0.39 0.42
9.
Chi-
chi_Taiwan-
03_1999
TCU 129
RSN1023 6.2 10.9 511 9.85 6.12 0.35 0.34
10.
Imperial
valley-1979
El centro
Array#4 RSN179 6.5 7.1 209 4.75 3.63 0.68 1.29

11.
Imperial
valley-
06_1979
El centro
Array#6
RSN181 6.5 1.4 203 5.19 3.76 0.66 1.22
12.
Imperial
valley-
06_1979
El centro
Array#10 RSN173 6.5 8.6 203 5.19 3.76 0.66 1.22
13.
Kocaeli,
Turkey_1999
Duzce
RSN1158 7.5 13.5 282 3.06 3.57 0.87 0.50
14.
Loma
Prieta_1989
Los Gatos -
Lexington
Dam
RSN3548 6.9 5.5 1070 4.34 4.04 0.89 0.98
15.
Denali,
Alaska_2002
TAPS Pump
Station#10
RSN2114 7.9 2.7 329 3.26 2.92 1.52 1.19
5. SYSTEM PARAMETERS
The variation of maximum displacement response may be influenced by several system parameters as well as loading
considerations for valuable conclusions. These primarily considerable two dynamic control parameters namely the lateral
natural period (Tx) and the uncoupled torsional-to-lateral period ratio (τ). This lateral periods (Tx) considered for symmetric
systems lies between 0.25 to 2.0 sec and for asymmetric system it considered 0.25 sec, 0.5 sec, 1.0sec and 2.0sec in short,
medium and long period ranges respectively. On the other hand, for most real buildings, the values of uncoupled torsional-to-
lateral period ratio (τ) are varied within the range of 0.25-2.0 with an interval of 0.05 also used in previous research [31, 33,
37]. Influence the torsional effect for asymmetric system eccentricity is important criteria to observe the critical response of
structural elements with respect on τ. Further, the present study attempts to incorporate the analysis of the bi-directional
asymmetric system into a feasible range of eccentric variation. In this case study, the three typical eccentricparametersofthis
system are classified in terms of small, intermediate and large eccentric systems as represented ase/D=0.05,0.1and0.2used
in previous literature [33, 37]. Hence, six combinations of eccentricity are considered along two principal directions in this
paper, as listed in Table 2. Asymmetric systems with stiffness and mass eccentricities areconsideredinthispresent study.The
four different values of ductility reduction factor (Rµ) = 2, 4 and 6 are chosen only for symmetric structure whereas standard
reduction factor Rµ = 4 select for asymmetric system only. Thesevaluesarehighlyrecommended bythedifferentcodes,suchas
ASCE 7-05 [36] and NEHRP [35].
Table 2: Combinations of eccentricity considered along two principal directions.
Sl. No. ex/D ey/D
1. 0.05 0.1
2. 0.05 0.2
3. 0.05 0.05
4. 0.2 0.2
5. 0.1 0.1
6. 0.1 0.2
Note: ex and ey are eccentricity in x and y-axis respectively.
6. RESULTS AND DISCUSSION
The nonlinear dynamic analysis of different story diagrid structures that are eleven story, twenty-one story and thirty-one
story systems through mean element displacement (for Rμ=2, 4 and 6) for various angle of braces (35°, 45° and 55°) is
presented with plotting as representative of the trend for both cases with the time variation lies between small tolargelateral
period that is 0.25sec to 2.0sec for symmetric system. Fig. [5-7] shows the mean displacement for various model structure in
different story at small, intermediate and large brace angles obtained by nonlinear dynamic analysis for square diagrid plan

On the other scenario, story drift one of the significant criteria for the assessment in drift demand of different story buildings
under ground motions excitation are presented in Fig. [11] for square diagrid system and Fig. [12] represented for circular
diagrid structural system. Fig. [11] indicates the response of drift demand for square symmetric configuration may be 0.0032,
0.0026 and 0.0024 times, whereas for circular section response indicates 0.0029,0.0023,and0.002timesrespectivelyshowin
Fig. [12]. In this case, structures are revealed that the increase in drift demand 0.0005, 0.0003 and 0.0004 times for both case
section and as well as another part show in Fig. [8-10] for tube type analysis model structurewith a circularplanshape. Fig.[5]
indicates the amplification in response for square symmetric configuration may be 1.8, 1.5 and 1.1 times,whereas,forcircular
section response indicates 1.5, 1.3, and 0.9 times respectively for Rμ=2 show in Fig. [8]. Influence of ground motion
characteristics on the nonlinear dynamic seismic response of symmetric diagrid structural system is systematically examined
to achieve a fair insight into the behavior of such systems. Fig. [6] indicates the amplificationinresponseforsquare symmetric
configuration may be 2.6, 2.3 and 2.1 times, whereas, for circular section response indicates 2.3,1.9,and1.6times respectively
for Rμ=4 show in Fig. [9]. Fig. [7] indicates the amplification in response for square symmetric configuration may be 4.2, 3.9
and 3.5 times, whereas, for circular section response indicates 3.8, 3.6, and 3.4 times respectively for Rμ=6 show in Fig. [10].
Fig. [5] and Fig. [8] reveal that the increase in displacement response 0.35, 0.31, and 0.2 times for bi-directional excitation for
Rμ=2. Fig. [6] and Fig. [9] reveal that the increase in displacement response 0.42, 0.4, and0.5timesfor bi-directional excitation
for Rμ=4, where torsional to lateral period ratio (τ) is negligible for zero eccentric condition.Finally, Fig.[7]andFig.[10]reveal
that the increase in displacement response 0.41, 0.32, and 0.1 times for bi-directional excitation for Rμ=6.
studies. It can be observed that as the slope of the braces increases, the mean value of the maximum drift also decreasesthatis
also satisfactory for displacement demand. In the structures with brace slope of a 35° and45°,thedisplacementandmaximum
drifts demand in the higher few stories are significantly larger due to the participation of the higher mode effectsfor both case
studies. Drift demand is being maximum at top story if the diagrid inclination angle is being minimum. Furthermore, drift
demand in intermediate story is being maximum for minimum diagrid angle, whereas in low story it varies show in Fig. [11-
12]. On the other scenario, mean of normalized responsearecomputedandpresentedforcornerelementsaremore vulnerable
Fig. 5. Mean displacement response of square diagrid system for (a) 35°, (b) 45°, (c) 55° brace angles (Rµ = 2).

due to lateral and torsional coupling effect in asymmetric structure.ThesecornerfourelementsElement1 isflexiblealongboth
principal directions and designated as “flexible, flexible”. Element 2 and Element 4 are combined as flexible and stiff for
different principal axis, designated as “flexible, stiff” and “stiff, flexible” respectively. Element 3 is stiff along both principal
direction and finally designated as “stiff, stiff”. The response of all corner elements are developed for physical understanding
due to bi-directional system of asymmetry. The considarable lateral periods for small, medium and large time history clearly
Fig. 8. Mean displacement response of circular diagrid system for (a) 35°, (b) 45°, (c) 55° brace angles (Rµ = 2).

plotted in Fig. [13-16] also dependent on ductility reduction factor (Rμ)=4 for obtaining the critical inelastic response in zone
IV at 55° standard brace angle. Fig, [13-16] has four sets of graphs shows the mean of response for a different combination of
bi-directional eccentric system. In these hybrid steel-concrete structural model indicates the dynamic response upto 2 to 3.1
times for 0.25sec, 2.3 to 3.2 times for 0.5sec, 2.9 to 3.5 times for 1sec, 3.1 to 3.65 times for 2sec respect to torsional effect and
Fig. 11. Drift demand of square diagrid system for (a) 35°, (b) 45°, (c) 55° brace angles.

Fig. 12. Drift demand of circular diagrid system for (a) 35°, (b) 45°, (c) 55° brace angles.
variation of stiffness-mass eccentric condition. Considering lateral period 0.25sec, the 1st Element maximum deformationlies
3.1 times and minimum 2 times for 3rd Element. In that case, Element 2 and 4 carries the almost same response that lies
Fig. 13. Mean displacement response of asymmetric diagrid system for T=0.25 sec at 55° brace angle (Rµ = 4).

Fig. 14. Mean displacement response of asymmetric diagrid system for T=0.5sec at 55° brace angle (Rμ=4).

between 2.2-2.4 shown in Fig. [13]. Furthermore,considering lateral period0.5sec,the Element1liesmaximumdeformationat
3.2 times and minimum 2.3 times for Element 4. Element 2 and 3 carries the average inelastic demand lies between 2.5-3.1
shown in Fig. [14]. For lateral time 1sec, the element 2 lies maximum deformation at 3.5 times and minimum 2.9 times for
Element 3. Element 1 and 4 obtain the demand lies between 3.2-3.4 times shown in Fig. [15]. Fig. [16] shows the maximum
Element 1 deformation for 3.65 times whereas minimum carried out for Element 4 at 3.1 times. Element 2 and 3 shows the
displacement between 3.3-3.4 times that near about same. In this context, it is neededtoobservefrom15earthquakedata that
is plotted for two different extreme combinations of eccentricities along X and Y directions. However, in this point, the
observation for inelastic seismic response of asymmetric diagrid system in small to large combination of different eccentric
conditions that assemble an effective scenario in seismic zone IV for suitability.
7. CONCLUSIONS
The present investigation analyzes the inelastic seismic performance of different story diagrid symmetric and asymmetric
model plan structures with various angle of braces are evaluated under critical seismic zone IV inIndia owingto bi-directional
NF ground excitation. The results are also indicated tocomparetheperformance with squareplandiagridstructurestocircular
model plan diagrid structures for the suitability in critical seismic zone IV in India. Also, the asymmetric systems have been
attempted the performance analysis for better understanding of serviceability. The following broad conclusions emerge.
1. The strong vulnerability of grid structural load resisting elements due to the bi-directional ground motion clearly
shows that the elements are less amount of losses on lateral periods than R/C structural system. The response of
structures for both case studies indicate that the higher overstrengthwithsmallerductility,dependsoncritical angle
of braces. Further, the seismic demand of elements appears to vary irregularly, as a result the story wisevariationof
both systems varies similarly. In thisstudy,dynamicobservationappearsto bemoreimportantfromtheviewpointof
mechanics.
2. Consideration of symmetric configuration effect owing to simultaneous bidirectional shaking may produce the
inelastic demand. The result analysis implies for both cases amplifies the response considerably. The structural
deformation of the square diagrid system is higher than circular system with respect to the lateral periods. On the
other hand, story drift demandclearly demonstrates thatthehigherdemandingvalues,significantlyscatter randomly
on higher story level than lower story. In that case, drift demand is maximum for square system that influences the
inelastic response of higher modal effect. The bird’s eyeobservation representstheperformanceofcircularsystem is
better than square system due to ground excitation.
3. The diagrid structure with the brace angle between 50° to 60° seemsthatitisresistingtobemoreefficientwithlateral
loads as well as gravitational easily in zone IV. Also, it is demonstrated that this standard brace angle is suitable for
any asymmetric system. Brace angle between 40°-50° is acceptable for square and circularsystemsthatcontrolsthe
large number of deformation and drift demand. In this diagridstructural systemM25gradeofconcreteissuitablefor
light weight of elements and also steel grid section is preferablewithpin-jointconnectionforflexibilitythanconcrete
grid joint connection.
4. Consideration of bi-directional interaction for asymmetric diagridsystem mayproducehigherinelasticdemand. With
increasing the uncoupled lateral period of structure, decreasing the inelastic range for such flexiblesystems andlies
constant. The response of asymmetric system at 55° brace angle lucidly concludes that the response due to bi-
directional ground motion obtains a major effectiveness of load resisting elements under the variation of eccentric
conditions in zone IV. The elemental deformation for large brace angle lies between 50°-60° consider as suitable for
zone IV, relaxing modal effect in random vibration.
Thus, the present paper may be helpful in the process of response analysis of the built or to-be-built structures in the event of
any anticipated earthquake prone and believe to be new. Safety level of the structures are undergoing seismic excitation
without collapse may be assessed to plan for the post-earthquake strategy. Such a symmetric and asymmetric diagrid plan
structures serve various functional and architectural requirements due to plan and interconnection activities leads to the
additional vulnerability of system. Furthermore, the sensitivity of the bi-directionally attacking forces execute the seismic
deterioration of such systems. This present paper may prove useful to provide broad guidelines to address all essential issues
and to highlight the needs for investigating the same in further details. These results can, therefore, help to evaluate the
retrofitting assessment due to additional strength demand. These findings point out the limitation of currentcodes developed
primarily on research in this particular aspect that employed a multi-story model. Hence, this interesting study may be
extended to assess the soil-structure interaction effect for asymmetric diagrid structural system obtaining further insight.

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